The inventive subject matter relates to memory devices and methods of operating the same and, more particularly, to memory devices using multiple memories connected to a common data input/output line and methods of operating the same.
Semiconductor memory devices may be classified as volatile semiconductor memory devices or nonvolatile semiconductor memory devices. Nonvolatile semiconductor memory devices may retain data stored therein when powered off. Data storage in nonvolatile semiconductor memory devices may be permanent or reprogrammable, depending upon the fabrication technology used.
A flash memory device is one type of nonvolatile memory device. Flash memory devices are widely used as voice and image data storage media in information processing devices, such as solid state drives, computers, handheld telephones, smart phones, digital cameras, camcorders, voice recorders, MP3 players, PDAs, handheld PCs, game consoles, facsimile machines, scanners, and printers. For the past several years, techniques have been developed to provide high-capacity, high-speed input/output and low-power nonvolatile memory devices in solid state drives or mobile devices (e.g., smart phones).
High-capacity and high-speed input/output solutions may be achieved by means of multi-stack chip packages wherein a plurality of nonvolatile memories are connected through the same channel. Reliability of such a data storage system may be reduced due to resistance and parasitic capacitance of unselected nonvolatile memories when performing a read, write or copy-back operation on a selected device. The parasitic capacitance may be reduced by increasing a driving force, which may cause overshoot and undershoot problems.
Thus, a measured capacitance value of a channel needs to be adjusted to correspond to a reference capacitance value defined in the specification to improve signal integrity.